The present invention relates to semiconductor devices and, more particularly, to semiconductor devices in which fine contact portions to connect elements with conductive wires are formed in the surface portion of a semiconductive substrate on which an integrated circuit is formed.
In recent years, the degree of integration of semiconductor integrated circuit devices has been improving every year and the number of elements formed on one chip has rapidly increased. A larger number of elements (for example, transistors) are proportionally reduced in size and mounted on a chip of a constant size. Therefore, the size of each element is decreased in inverse proportion to the increase in integration.
Theoretically, as the size of element such as a transistor decreases, the length of the carrier movement path in the substrate is reduced, increasing the operating speed of the integrated circuit. However, practically speaking, the parasitic resistance components in the wiring pattern and contact portion increase with the increase in integration, and, consequently, the improvement in operating speed of the integrated circuit is less than theoretically expected. For instance, when the size of the contact hole is reduced, the substantial contact resistance increases in the connecting portion through the contact hole between the element formed on the substrate and the connecting wire. Thus, the current driving capability in each element is suppressed and the electrical characteristics of the integrated circuit which has fine elements will be degraded. With this technical background, there is a certain limitation in the improvement in integration of the integrated circuit due to a reduction in scale.
Further, with a conventional semiconductor device, since the interface of the metal-semiconductor junction in the contact region is the flat surface, a current flowing from the connecting wire in the contact region to the element is concentrated at the edge portion of the contact surface (this state is called current crowding effect). Thus, good current supply in the contact region is obstructed.